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%I #4 Mar 18 2013 12:39:27
%S 6,10,18,20,22,27,34,40,49,52,58,64,68,82,98,100,118,136,142,144,148,
%T 160,162,164,202,212,214,242,243,244,274,288,289,298,320,325,333,338,
%U 343,356,358,361,382,392,394,404,436,441,454,464,478,512,538,544,548
%N sigma(n) - phi(n) gives a semiprime (A001358).
%H Harvey P. Dale, <a href="/A116001/b116001.txt">Table of n, a(n) for n = 1..1000</a>
%e sigma(100)-phi(100)=177=3*59
%t Select[Range[600],PrimeOmega[DivisorSigma[1,#]-EulerPhi[#]]==2&] (* _Harvey P. Dale_, Mar 18 2013 *)
%Y Cf. A001358, A116017, A116000.
%K nonn
%O 1,1
%A _Giovanni Resta_, Feb 13 2006
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